Researchers have created a genetic map of the UK and Ireland, revealing links between Gaelic lands and Iceland.

A new study published to the journal Proceedings of the National Academy of Science has revealed the first comprehensive genomic analysis of Scotland based on DNA from 2,500 people. These people have extended ancestry from specific regions across Great Britain and Ireland, with research led by the Royal College of Surgeons in Ireland (RCSI) and the University of Edinburgh.

The study was able to show strong genetic connections between the Scots and Norse Vikings, shedding light on the Gaelic component to the Icelandic gene pool. This new research marks the first time the genetic map of the UK and Ireland can be seen in its entirety.

At least six clusters of genetically similar individuals can be placed on a map of Scotland: the borders, the south-west, the north-east, the Hebrides, Orkney and Shetland. Some of these clusters – notably those linked with the south-west and the Hebrides – share particularly strong affinity for clusters of Irish ancestry.

The researchers said that the clusters were closely linked to Dark Age kingdoms such as Strathclyde in the south-west, Pictland in the north-east and Gododdin in the south-east. This suggests that these ancient states may have maintained regional identities that remain today.

A map of the genetic landscape of Ireland and Britain using 2,554 individuals with regional ancestry grouped by 43 clusters. Left: A tree of the 43 different genetic clusters grouped on branches by similarity. Right: The geographic coordinates of the ancestral birthplace of 2,429 Irish or British individuals, coloured coded by genetic cluster. Image: Gilbert/PNAS/RCSI

Unique Donegal

Shetland – an archipelago of approximately 100 islands located between Scotland and Norway – was found to harbour the largest proportion of Norwegian-related ancestry, a consequence of the Norse Viking migrations that began in the eighth century.

This study compared the genomes of ancient Celts buried in Iceland to the modern genetic diversity in Britain and Ireland. The results showed that Iceland’s ancient settlers share the greatest genetic affinity with those found on the Western Isles of Scotland and Ireland’s north-west.

With Ireland, this makes Donegal the most genetically isolated region of Ireland seen to date, with little evidence of the migrations that affected the rest of Ulster.

“This work is important not only from the historical perspective, but also for helping understand the role of genetic variation in human disease,” said Dr Edmund Gilbert of RCSI, lead author of the paper.

“Understanding the fine scale genetic structure of a population helps researchers better separate disease-causing genetic variation from that which occurs naturally in the British and Irish populations, but has little or no impact on disease risk.”